1. Field of the Invention
The present invention relates to an axial flow fan.
2. Description of the Related Art
In recent years, various electronic equipments have been becoming smaller and smaller. Also, the amount of heat generated by electronic devices in the electronic equipments has been greater. However, such devices fail if temperature of their electronic equipments or processor units becomes too high. Therefore, a fan which is usually arranged inside an electronic device is typically used to cool the electronic components and processor units of the electronic device.
For example, an axial flow fan is often used to cool the electronic components and processor units of the electronic device. The axial flow fan typically includes a housing which accommodates therein an impeller which rotates centered about the central axis thereof. The impeller typically includes a cup having a substantially cylindrical shape, and a plurality of rotor blades each extending radially outwardly. When the impeller rotates, an air flow is generated flowing along the axial direction.
Generally, the axial flow fan is expected to generate a large quantity of air flow having a high static pressure. In order to increase the quantity of air flow, for example, a number of rotations of the impeller may be increased. On the other hand, in order to increase the static pressure of the air flow, a stator blade or a plurality thereof may be arranged at an outlet side of the axial flow fan.
The stator blades are usually arranged so as to adjust the air flow generated by the rotation of the impeller. The air flow typically includes an axial flow component, a swirling flow component centered about the central axis, and a centrifugal component of the air flow flowing in the axial direction. When the air flow makes contact with the stator blade, the swirling flow component of the air flow is adjusted to the axial flow component, whereby the static pressure of the air flow is improved.
However, the dimension and shape of the stator blade needs to be adjusted in accordance with the quantity of the air flow flowing through the housing. In general, the quantity of air flow flowing near the area of the cup of the impeller is smaller than that flowing near a radially outer area of the rotor blade.
Also, since the air flow generated by the rotation of the impeller includes the swirling flow component and the centrifugal component, when the air flow is outletted from the housing, the air flow will spread radially outwardly. When the air flow spreads radially outwardly, the fan does not effectively cool the heated electronic components and processor units of an electronic device.